fwsnort: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/sbin/fwsnort - from package: fwsnort

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/fwsnort - from package: fwsnort

You may install the required package with command apt-get install {package}

Error in other languages:
fwsnort: bevel nie gevind nie
fwsnort: comandă negăsită
fwsnort: comando não encontrado
fwsnort: commande introuvable
fwsnort: command not found
fwsnort: käsku ei ole
fwsnort: không tìm thấy lệnh
fwsnort: komanda nerasta
fwsnort: Kommando nicht gefunden.
fwsnort: kommandot finns inte
fwsnort: komut yok
fwsnort: nie znaleziono polecenia
fwsnort: níor aimsíodh an t-ordú
fwsnort: no se encontró la orden
fwsnort: no s'ha trobat l'ordre
fwsnort: opdracht niet gevonden
fwsnort: parancs nem található
fwsnort: perintah tidak ditemukan
fwsnort: príkaz nenájdený
fwsnort: příkaz nenalezen
fwsnort: команда не найдена
fwsnort: командата не е открита
fwsnort: 命令找不到
fwsnort: コマンドが見つかりません